1. Field of the Invention
The present invention relates to a liquid ejection head and an image forming apparatus, and more particularly, to a composition of a liquid ejection head which is suitable for an inkjet recording head, or the like, which changes a volume of a pressure chamber by driving a piezoelectric element in order to eject a liquid droplet, and to an image forming apparatus using same.
2. Description of the Related Art
In an inkjet recording head using piezoelectric elements, it is necessary to control the driving of the piezoelectric elements in consideration of the Helmholtz resonance frequency of the pressure chambers. For example, Japanese Patent Application Publication No. 8-290571 discloses that ink droplets having a virtually spherical shape are generated by using an inkjet recording head in which the inertance Mn of a nozzle aperture and the inertance Ms of the ink supply aperture satisfies “Mn/(Mn+Ms)>0.5”. Moreover, Japanese Patent Application Publication No. 8-290571 proposes that high-speed driving is achieved by setting the contraction time of a piezoelectric oscillator for suctioning ink into a pressure generating chamber (pressure chamber), and the expansion time of the piezoelectric element for ejecting an ink droplet from the nozzle aperture, to 1/f (where f is the Helmholtz resonance frequency). The residual vibration of the meniscus is thus reduced as far as possible.
However, Japanese Patent Application Publication No. 8-290571 refers only to the inertance ratio (Mn/(Mn+Ms)) and the Helmholtz resonance frequency, and it does not refer to the ejection speed for ejecting liquid droplets. In general, when ejection force is enlarged, not only does the ejection speed of the ejected liquid droplet (main droplet) increase accordingly, but also a large number of satellite droplets are generated.
Since these satellite droplets cause image deterioration, then the occurrence of a large number of satellite droplets is not desirable from the viewpoint of image quality. In Japanese Patent Application Publication No. 8-290571, the occurrence of satellite droplets is not considered, and there is a possibility that image quality may deteriorate due to the occurrence of a large number of satellite droplets.